1. Field of the Invention
The present invention relates to a dial needle with indexed angular position, for mounting on the output shaft of a drive element of a measuring instrument, comprising a body with a pointer and a holding foot adapted to be fixed to the shaft for rotational and translational movements, by one of its sides, the body being adapted for fixing removably to the shaft for translational movement and indexed in angular position on the holding foot, by its other side.
A dial needle is intended to be driven by an element of an instrument measuring a physical magnitude, which element is itself driven with a movement representative of the value of this magnitude, in front of a dial carrying divisions of a graduation, for indicating the value of this magnitude. Generally, such a needle is mounted on the shaft of a rotary motor.
It will be readily understood that calibration of the motor and of the measuring instrument must be carried out with the needle mounted on the motor and before the dial of the instrument is in position, after fixing, to an instrument panel. Subsequent adjustment of the motor and of the instrument must moreover take place under the same conditions. Since the needle must be removed for fixing the dial to the instrument panel, that means that after fixing the dial the needle may take up its angular calibrated and adjusted position.
2. Description of the Prior Art
A dial needle of the above mentioned type is known from the document FR-A-86 02153. Its needle body may be separated from the holding foot after calibration then re-positioned in the initial angular indexation. Indexing of the needle body on the holding foot is here achieved by keying on a portion of the foot which is asymmetric with respect to the axis of the shaft. More precisely, the keying portion of the holding foot comprises two resilient tongues disposed on each side of this axis and having teeth for fixing the needle body on the holding foot for translational movement.
The needle of document FR-A-86 02153, apart from the fact that its accuracy leaves much to be desired because of the arrangement, with respect to the axis of the holding foot, of the tongues for indexing and fixing the needle body for translational movement is relatively difficult to produce.
The document GB-A-1 556 284 also teaches a dial needle, of a type closely related to that mentioned above, not in two but in three parts. Furthermore, these parts are even more difficult to manufacture than those of the preceding document and fixing of the holding foot for rotation on the output shaft and the angular indexing of the needle body are here obtained by means which are just as complex such as a pawl or a spring mounted ball.